The long term goal is to identify molecular targets that can be used for prognosis and therapy of HNSCC. Head & neck squamous cell carcinomas (HNSCC) represent the 6th most common cancer type in western countries. The major HNSCC etiological factors are environmental carcinogens, e.g., tobacco and alcohol, which cause genetic alterations and chronic inflammation in head & neck (H&N) tissues. In this application, we will use an inducible H&N-specific gene targeting system to introduce several genetic alterations in the TGF signaling pathway, which are common in human HNSCC, into mouse H&N tissues, and assess the mechanisms by which these alterations promote HNSCC development. Aim 1 will examine molecular mechanisms of Smad4 loss-mediated HNSCC development. We will assess if any Fanc/Brca members are direct Smad4 transcriptional targets, and if VEGF overexpression in Smad4-/- HNSCCs is the result of Smad3 activation and contributes to Smad4 loss-mediated HNSCC carcinogenesis. Genome-wide analyses will be performed to identify additional alterations caused by Smad4 loss, which contribute to oncogenic effects on H&N epithelia and stroma. Aim 2 will assess the role of Smad2 loss in HNSCC promotion. We will determine if Smad2 loss promotes HNSCC formation and progression in the presence of a Kras mutation. We will analyze if increased HGF signaling found in Smad2-/- tissues contributes to Smad2 loss-associated oncogenic effects and study the mechanisms of HGF upregulation in Smad2-/- cells. Genome-wide screens will also be performed to identify molecular alterations caused by Smad2 loss in H&N tissues. Aim 3 will assess the role of stromal TGFRII loss in HNSCC development. We will induce TGFRII deletion in oral fibroblasts to ascertain if this will induce or promote HNSCC formation in the presence of either a chemical carcinogen-induced H-ras mutation or TGFRII deletion in H&N epithelia. Pathological and molecular alterations caused by oral fibroblast TGFRII deletion will be analyzed. These studies will not only improve our understanding of HNSCC biology, but will also directly test therapeutic approaches in HSNCC with specific TGF signaling defects.